In preparation for the upcoming syncrepl changes, I've updated liblutil
to generate CSNs with microseconds in the timestamp.

Currently slapd copies the entryCSN timestamp to the createTimestamp and
modifyTimestamp attributes when generating these attributes. Anyone have
any thoughts on whether it would be a too-surprising change for these
attributes to now have higher resolution? Should we keep truncating them
to 1-second resolution?

Maybe we should carefully check that appropriately sized buffers are
used everywhere in the code, to avoid surprises... this could be a good
chance to make sure generalizedTime is handled in exactly one place
(which could already be, didn't check recently).